1. Field of the Invention
The present invention relates to a liquid-droplet jetting apparatus which jets liquid from a nozzle.
2. Description of Related Art
An ink-jet head is an apparatus which jets liquid droplets of ink from nozzles onto an object such as recording paper. In the ink-jet head, however, when the nozzles are clogged due to dust and/or the ink with increased viscosity or when any air bubbles enter in an ink channel including the nozzles, the jetting characteristics of the nozzles (such as a volume of jetted liquid-droplets and a flying direction of liquid droplets) become abnormal in some case, and further, the ink cannot be jetted from the nozzles at all in other cases. For this reason, when the ink cannot be jetted from the nozzles normally, an ink-jet head of general type has a construction for performing an operation (so-called purge operation) to forcibly jet the ink from the nozzles to discharge (purge) the dust and/or air bubbles, thereby resolving the abnormality in the ink-jetting operation.
For example, Japanese Patent Application Laid-open No. 05-220970 describes an ink-jet head (printing head) including a cap (capping member) which can be attached to an ink-jetting surface so as to cover jetting ports of nozzles, and a suction pump connected to the cap via a tube. In a state that the cap is attached to the ink-jetting surface, the suction pump sucks the ink from the nozzles to forcibly jet the ink into a space within the cap, thereby making it possible to resolve the abnormal state in the ink-jetting head.
During the purge operation, however, a part or portion of the ink, which flows out of the nozzles and is in a bubbled state, is easily adhered to a portion in the vicinity of jetting ports in the ink-jetting surface. Further, since the inside of the ink-jet head is maintained at negative pressure, there is a fear that the bubbled ink returns to the inside of nozzles and any bubbles enter in the nozzles, thereby again causing the abnormal state in which the ink cannot be jetted in a normal manner from the nozzles. In addition, in order to recover the ink sucked by a suction pump or the like during a purge operation to reuse (recycle) the ink, a complex structure such as a tube connecting the cap and a sub tank for the ink provided in a movable ink-jet head is needed. Therefore, the sucked ink has been wasted (discarded) in a wasted ink chamber without being reused
An object of the present invention is to provide a liquid-droplet jetting apparatus which is capable of preventing, as much as possible, the ink flowing out of the jetting nozzles during purge operation from adhering to a portion in the vicinity of the jetting ports of the jetting nozzles.
According to a first aspect of the present invention, there is provided a liquid-droplet jetting apparatus which jets a liquid in a liquid-droplet state, the liquid-droplet jetting apparatus including:                a channel unit including a jetting nozzle, a jetting channel communicating with the jetting nozzle, a recovery nozzle, a recovery channel communicating with the recovery nozzle, and a liquid-droplet jetting surface in which a jetting port and a recovery port are formed as an opening of the jetting nozzle and an opening of the recovery nozzle, respectively;        a jetting-pressure applying mechanism which applies jetting pressure to the liquid in the jetting channel;        a cap which detachably covers both of the jetting port of the jetting nozzle and the recovery port of the recovery nozzle; and        a purge pressure applying mechanism which causes the liquid in the jetting channel to flow to the recovery channel when the cap covers both of the jetting port and the recovery port;        wherein the liquid is flowed out from the jetting port to be recovered from the recovery port to the recovery channel by the purge pressure applying mechanism. Further, the recovery port of the recovery nozzle may be formed, in the liquid-droplet jetting surface, adjacent to the jetting port of the jetting nozzle.        
According to the first aspect of the present invention, when a jetting pressure is applied to the liquid in the jetting channel by the jetting-pressure applying mechanism, the liquid is jetted from the jetting nozzle communicating with the jetting channel. On the other hand, when the jetting of the liquid from the jetting nozzle become abnormal due to the clog-up of the jetting nozzle and/or air bubble entered in the jetting channel, or the like, the liquid in the jetting channel is flowed out from the jetting nozzle, for example, to the space between the cap and the liquid-droplet jetting surface by the purge pressure applying means, in a state that the cap covers the jetting port of the jetting nozzle.
Here, for example, the recovery nozzle is formed at a portion in the vicinity of the jetting nozzle, and the recovery port of the recovery nozzle may be provided adjacent to the jetting port of the jetting nozzle. Furthermore, when the jetting nozzle is purged, the jetting port of the jetting nozzle and the recovery port of the recovery nozzle are sealed and covered by one cap. Accordingly, the liquid flowed out of the jetting nozzle can be recovered from the space between the cap and the liquid-droplet jetting surface, via the recovery nozzle to the recovery channel. Therefore, a substantial part of the liquid bubbled when being flowed out from the jetting nozzle is recovered and hardly adheres to the liquid-droplet jetting surface, and thus an amount of the liquid, adhered to a portion in the vicinity of the jetting nozzle in the liquid-droplet jetting surface, becomes small. Accordingly, it is possible to prevent, as much as possible, the liquid, which is bubbled when being flowed out of the jetting nozzle, from returning to the inside of the jetting nozzle and causing any jetting abnormality of the nozzle.
In the liquid-droplet jetting apparatus of the present invention, the purge pressure applying mechanism may include a suction unit which performs sucking from a side of the recovery channel to depressurize a space formed between the cap and the liquid-droplet jetting surface. Accordingly, by depressurizing the space between the cap and the liquid-droplet jetting surface by the sucking unit, it is possible to perform purge for the jetting nozzle by making the liquid flow out from the jetting port of the jetting nozzle to the space between the cap and the liquid-droplet jetting surface, and to recover the flowed-out liquid from the recovery nozzle to the recovery channel.
In the liquid-droplet jetting apparatus of the present invention, the purge pressure applying mechanism may further include a pressurizing unit which pressurizes the liquid in the jetting channel. According to this construction, during the purge for the jetting nozzle, it is possible to increase a speed at which the liquid is flowed out by pressurizing the liquid in the jetting channel with the pressurizing unit, thereby performing the purging assuredly.
In the liquid-droplet jetting apparatus of the present invention, the recovery nozzle may include a plurality of individual recovery nozzles, the individual nozzles having individual recovery ports respectively, the individual recovery ports being openings of the individual recovery ports; and two individual recovery ports included in the individual recovery ports may be arranged in the liquid-droplet jetting surface at positions opposite to each other with respect to the jetting port. According to this construction, since the liquid flowed out of the jetting port of the jetting nozzle is recovered assuredly by the individual recovery ports, of the individual recovery nozzles, arranged on both sides respectively of the jetting port, it is possible to further reduce an amount of the liquid adhered to a portion in the vicinity of the jetting port.
In the liquid-droplet jetting apparatus of the present invention, the jetting nozzle of the channel unit may include a plurality of individual jetting nozzles; the recovery nozzle of the channel unit may include a plurality of individual recovery nozzles; and individual jetting ports which are openings of the individual jetting nozzles and individual recovery ports which are openings of the individual recovery nozzles may be formed in the liquid-droplet jetting surface. By forming the plurality of individual jetting nozzles and the plurality of individual recovery nozzles in the channel unit, it is possible to jet and recover the liquid in a substantial amount at a time.
In the liquid-droplet jetting apparatus of the present invention, the individual jetting ports may be aligned in a predetermined direction in the liquid-droplet jetting surface; and each of the individual recovery ports may be arranged between the individual jetting ports. According to this construction, the liquid flowed out from two individual jetting ports can be recovered from an individual recovery port arranged between these two individual jetting ports, thereby reducing the number of individual recovery ports. In addition, it is possible to arrange the individual recovery ports densely, thereby leading to miniaturization of the apparatus.
In the liquid-droplet jetting apparatus of the present invention, the individual jetting ports may be aligned in a row in a predetermined direction in the liquid-droplet jetting surface; and                the individual recovery ports may be aligned in rows parallel to a direction in which the individual jetting ports are aligned, the rows of the individual recovery ports being at both sides the row of the individual jetting ports. According to this construction, the liquid flowed out from the individual jetting ports can be recovered assuredly from the individual recovery ports aligned at both sides of the individual jetting ports, and amount of the liquid adhered to portions in the vicinity of the individual jetting ports can be reduced.        
In the liquid-droplet jetting apparatus of the present invention, the individual jetting ports may be aligned in a plurality of rows along a predetermined direction and at a predetermined pitch in the liquid-droplet jetting surface;                an individual jetting port, belonging to one of two adjacent rows included in the rows of the individual jetting ports, may be arranged in the predetermined direction to be shifted by a half of the pitch relative to another individual jetting port belonging to the other of the two adjacent rows of the individual jetting ports;        the individual recovery ports may be aligned, between the two adjacent rows of the individual jetting ports, along the predetermined direction and at the predetermined pitch; and        each of the individual recovery ports may be positioned on a line connecting two individual jetting ports belonging to the two rows of the individual jetting ports, respectively, and which are arranged in the predetermined direction to be shifted from each other by the half of the pitch, the two rows of the individual jetting ports being aligned on both sides, respectively, of the individual recovery ports. According to this construction, during the purge operation, the liquid flowed out from the individual jetting nozzles can be recovered effectively with the individual recovery nozzles which number is half of that of the individual jetting nozzles. Therefore, it is possible to secure a wide area at which the individual jetting nozzles are arranged, thereby arranging the individual jetting nozzles highly densely to miniaturize the liquid-droplet jetting apparatus.        
The liquid-droplet jetting apparatus of the present invention may have a communication section which communicates the jetting channel and the recovery channel in an outside of the channel unit. According to this construction, the liquid flowed out from the jetting nozzle during the purge operation can be recovered from the recovery nozzle, and then the liquid can be returned to the jetting channel via the communication section, thereby making it possible to reuse (recycle) the liquid.
In the liquid-droplet jetting apparatus of the present invention, the communication section may be provided with a filter which removes a foreign substance existing in the liquid recovered from the recovery channel. According to this construction, any foreign substance existing in the recovered liquid can be removed by the filter before the recovered liquid is returned to the jetting channel. Therefore, it is possible to prevent the foreign matter from flowing into the jetting channel and to cause the clog-up of the jetting nozzle.
In the liquid-droplet jetting apparatus of the present invention, the communication section may have a storage portion which stores the liquid recovered from the recovery channel; and the filter may be provided in the storage portion. According to this construction, the liquid, flowed from the recovery channel to the storage portion, passes through the filter in the storage portion so that the foreign substance is removed from the liquid, and then the liquid flows into the jetting channel. Therefore, it is possible to prevent the foreign substance from flowing into the jetting channel and to cause the clog-up of the jetting nozzle.
In the liquid-droplet jetting apparatus of the present invention, the liquid recovered from the recovery channel may be jetted from the jetting nozzle via the jetting channel. In this case, the liquid, which has been recovered from the recovery channel can be circulated to be jetted again, an amount of the discarded liquid can be reduced. For example, when the liquid-droplet jetting apparatus is an ink-jet printer, the amount of ink, discarded during the purge operation of the head, can be drastically reduced. Accordingly, there is no need to provide in the inside of the printer a discarded liquid chamber to which the ink is discarded. In addition, since there is no need to estimate an amount of ink to be discarded during purge operation in advance, it is possible to reduce an amount of the ink, which is substantially necessary for performing printing onto a predetermined number of paper sheets or the like. Thus, a volume of the ink tank can be miniaturized.
In the liquid-droplet jetting apparatus of the present invention, liquid repellence of an area around the jetting port may be greater than that of an area around the recovery port in the liquid-droplet jetting surface. In this case, an amount of the liquid adhered to a portion around the jetting port can be reduced, thereby effectively recover the liquid adhered to a portion around the recovery port.
In the liquid-droplet jetting apparatus of the present invention, the cap may be partitioned into a plurality of areas, and each of the areas of the cap may independently cover the individual jetting ports and the individual recovery ports. In this case, it is possible to effectively recover the liquid by partitioning the cap into a plurality of areas in accordance with the arrangement of the individual jetting ports and individual recovery ports.
According to a second aspect of the present invention, there is provided a liquid-droplet jetting apparatus which jets a liquid in a liquid-droplet state, the liquid-droplet apparatus including:    a head including: a channel unit having a jetting nozzle, and a jetting channel communicating with the jetting nozzle; a maintenance mechanism which has a recovery nozzle and a recovery channel communicating with the recovery channel and which perform maintenance for the channel unit; and a liquid-droplet jetting surface formed with a jetting port and a recovery port as an opening of the jetting nozzle and an opening of the recovery nozzle, respectively;    a jetting pressure applying mechanism which applies jetting pressure to the liquid in the jetting channel;    a cap which detachably covers both of the jetting port of the jetting nozzle and the recovery port of the recovery nozzle; and    a purge-pressure applying mechanism which is fluidly connected to the recovery channel and which applies purge pressure to the liquid in the recovery channel;    wherein the liquid is flowed out from the jetting port to be recovered from the recovery port to the recovery channel by the purge pressure applying mechanism.
According to the second aspect of the present invention, the maintenance mechanism is provided to the head, and the cap and the maintenance mechanism are not integrally formed. Therefore, it is possible to miniaturize the area in which the cap of the liquid-droplet apparatus is arranged, thereby reducing a space for installing the liquid-droplet jetting apparatus.
In the present application, the term “purge pressure” means a pressure applied to the liquid or the like in the recovery channel so as to recover the liquid via the recovery channel, and is intended to include both negative pressure and positive pressure.